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Upward Showering Muons in Super-Kamiokande
Shantanu Desai /Alec HabigFor
Super-Kamiokande Collaboration
ICRC 2005 Pune
Upward Going Muons in Super-K
THRU
STOP
Eυ (GeV)
dΦ/d
logE
υ( 1
0-13 c
m-2
s-1
sr-1
)
ThrugoingStopping
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1 10 102
103
104
105
Muon Energy loss as a function of Energy
Distribution asymmetric for each muon energies
Reasonably good agreement of Monte-Carlo with PDG
Ei
EfL
dE/dX = (Ei - E
f)/L
Aim of this analysis is only to separate a given muon into showering/non-showering
Muon energy (GeV)
< d
E/dX
(MeV
cm
2 g-1
) >
Average < dE/dX > from M.C.
Ionization LossRadiative Loss
Total Loss
1
10
10 2
1 10 102
103
104
105
Showering Muon
(Groom et al 03)
Non-Showering muon
Muon track
PMT
dwat
Apply following correction for every PMT in Cherenkov Cone
qcorr
= qraw
dwat
exp(dwat
/Latten
)
-------------------------- F(θ)
where Latten
= Water attenuation length,
dwat
= Distance from PMT to point of
projection to µ track F(θ) = PMT acceptance + shadowing
Divide the muon track into 50 cm bins. For each bin, calculate average corrected charge and its error as follows:
Qcorri ��
1
N pmt qcorr
N pmt
where Npmt
= No of pmts within the given
projected distance corresponding to each bin
�Qcorri
2 �1
N pmt2 �
1
N pmt qcorr2
qraw
Corrections to raw PMT charge
Muon track
PMT
dwat
Apply following correction for every PMT in Cherenkov Cone
qcorr
= qraw
dwat
exp(dwat
/Latten
)
-------------------------- F(θ)
where Latten
= Water attenuation length,
dwat
= Distance from PMT to point of
projection to µ track F(θ) = PMT acceptance + shadowing
Divide the muon track into 50 cm bins. For each bin, calculate average corrected charge and its statistical error as follows:
Qcorri ��
1
N pmt qcorr
N pmt
where Npmt
= No of pmts within the given
projected distance corresponding to each bin
Corrections to raw PMT charge
�Qcorri
2 �1
N pmt2 �
1
N pmt qcorr2
qraw
Corrected Charge Distribution Comparison of ionizing vs showering muon
Projected Distance Along Track (m)
Mea
n co
rrec
ted
phot
o-el
ectr
ons
/ 0.5
m
0
10
20
30
40
50
60
70
80
90
0 2 4 6 8 10 12 14 16 18 20Projected Distance Along Track (m)
Mea
n co
rrec
ted
phot
o-el
ectr
ons
/ 0.5
m0
10
20
30
40
50
60
70
80
90
0 2 4 6 8 10 12 14 16 18 20
Muon Energy = 20 GeV Muon Energy = 10 TeV
dE/dX = 2.16 MeV/cm dE/dX = 8.5 MeV/cm
Both simulated muons have same entry point and direction
for a ionizing muon as a functionof path-length
Variables used for showering/non-showering separation
�2��i�3
n�2
��Qcorri ��Qcorr
2 ��Qcorri
2 �
where �Qcorr �
�4
n�3
Qcorri ��Qcorr
i
2
�4
n�3
1��Qcorri
2
q l ���Qcorr and
����Qcorr �q l �
{Shape Comparison
Difference in averagecorrected charge ofgiven muon – samefor ionzing muon
(Average corrected charge averaged over entire muon length)
{
Absolute Corrected Charge Comparison
log10 (Σ {(dE/dX)i- mean}2/dof)
No of
even
tsDataM.C.
0
100
200
300
400
500
600
0 0.5 1 1.5 2 2.5 3 3.5
DataMonte-Carlo
(∆m2 =0.002 sin2 2Θ =1.0)
[ mean qcorr - Q(L) ]
No of
even
ts
0
20
40
60
80
100
120
140
160
180
200
-4 -2 0 2 4 6 8 10
comparison
for data and monte-carlo
for data and monte-carloχ2
∆ comparison
Variables when appliedto 100yr upmu NEUT Monte-Carlo
SHOWERING CUT USED
χ2 /DOF>20 and ∆>2.5
χ2/DOF >30 and ∆ >2.0
χ2 /DOF>50 and ∆>0.5
∆ > 4.5
OR
OR
ORTotal no of showering events = 5575 (out of 37301) in 100 year upmu NEUT Monte-carlo
χ2/DOF >40 and ∆ >1.0
Efficiency = 71 % where,
Efficiency = No of events Identified by algorithm --------------------------------------------- No of events with ∆ E / ∆ X > 2.85 MeV/cm
∆ E = Energy deposited by muon in inner detector
∆ X = Length of muon in inner detector
OR
NEUTRINO ENERGY SPECTRA
Eυ (GeV)
dΦ/d
logE
υ( 1
0-13 c
m-2
s-1
sr-1
)
ShoweringNon-showeringStopping
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1 10 102
103
104
105
<Eυ> ~ 1 TeV
<Eυ> ~ 100 GeV
<Eυ> ~ 10 GeV
Super-KamiokandeRun 2101 Sub 3 Ev 1523996-07-05:01:46:37 0013 dee4 0606
Inner: 10877 hits, 191405 pE
Outer: 249 hits, 863 pE (in-time)
Trigger ID: 0x0b
D wall: 1690.0 cm
Upward-Going Muon Mode
Charge(pe) >26.723.3-26.720.2-23.317.3-20.214.7-17.312.2-14.710.0-12.2 8.0-10.0 6.2- 8.0 4.7- 6.2 3.3- 4.7 2.2- 3.3 1.3- 2.2 0.7- 1.3 0.2- 0.7 < 0.2
0 500 1000 1500 20000
400
800
1200
1600
2000
0 500 1000 1500 20000
400
800
1200
1600
2000
Times (ns)
Event Display of upward showering muon
Angular Resolution of showering muons
Shaded regioncontains 68 %of total area
Angular resolution = 1.25°
Thrugoing muons : Angular resolution ~ 1°
Stopping muons : Angular resolution ~ 1°
Angular resolution of Showering thrumus
Angle between precision fit and truth fit
No
of e
vent
s
0
50
100
150
200
250
300
350
400
0 1 2 3 4 5 6 7 8 9 10
µtrue
µfit
Zenith-angle distribution of showering muons
cosΘ
No o
f eve
nts
No Oscillation
∆m2 = 0.0025 sin2 2Θ =1.00
0
200
400
600
800
1000
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0
Showering muons relatively insenstive to oscillation ==> For this dataset chi-square for null -oscillation should be very good fit
Background SubtractionApplied the showering algorithm to horizontal thrugoing muonwith 0 < cos(θ)< 0.08
Azimuth distribution of all showering muons
Φ (degrees)
No
of E
vent
s
(1) (2) (1)
1
10
10 2
10 3
0 50 100 150 200 250 300 350
19.48 / 14P1 1.702 0.8869P2 1.728 0.7089P3 65.17 10.86
cosΘ
Num
ber o
f Eve
nts Region (1) Φ < 60 , Φ > 240
Region (2) 60 < Φ < 240
10-1
1
10
10 2
10 3
-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08
Nbkgd
= 8.63 +12-5
for cos(θ)> -0.1 (Asymmetric distribution because of bump near horizon)
Fit to thin rock zenith angle distribution: f[cos(θ)] = p1+ exp [p2+p3 cos(θ)]
Showering Muon Oscillation Results
Best-fit (physical region) : χ2 = 4.68 / 7 dof for (∆m2, sin22θ) = (0.0104 eV2, 0.9)
Best-fit (null oscillation) : χ2 = 6.51/9 dof
Zenith angle comparisonat best fit point
Null oscillation normalized by livetime
cosΘ
No of
show
ering
muo
ns
0
10
20
30
40
50
60
70
80
90
100
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0
Projections of chi-square distributions for showering muons
Null oscillation allowed even at 68 % confidence level as expectedfor this high energy ν
µ with mean energy of ~ 1 TeV
0
2
4
6
8
10
10-4
10-3
10-2
∆m2 (eV2)
χ2 - χ2 m
in
68% C.L.90% C.L.99% C.L.
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1 1.2 1.4
sin22θ
χ2 - χ
2 min
68% C.L.90% C.L.99% C.L.
Comparison with all upward thrugoing muons
0
2
4
6
8
10
10-4
10-3
10-2
∆m2 (eV2)
χ2 - χ2 m
in
68% C.L.90% C.L.99% C.L.
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1 1.2 1.4
sin22θχ2 -
χ2 min
68% C.L.90% C.L.99% C.L.
Best-fit : χ2 = 7.64 / 7 dof for (∆m2, sin22θ) = (0.0024 eV2, 0.96)
Best-fit at null oscillation : χ2 = 19.6/9 dof
Upward thrugoing muons sensitive to neutrino oscillation
CONCLUSIONS � A sample of upward thrugoing muons which lose energy through radiative processes have been identified.
� Mean energy of parent neutrinos of upward showering muons ~ 1 TeV.
� 5575 showering muons in 100yr neut Monte-carlo and 309 events in 1679.6 days data
� Zenith angle distribution of upward showering muons consistent with null oscillations
� This dataset will now be used for oscillation analysis with all datasets by providing an extra energy bin at highest energies.
� A variety of astrophysical searches with upward showering muons done. Nothing found. (S. Desai thesis 2003. Also A. Habig poster)